This invention relates generally to turbochargers for use with internal combustion engines, and, more particularly, to turbochargers having at least one flywheel assembly.
A limiting factor in the performance of an internal combustion engine is the amount of combustion air that can be delivered to the intake manifold for combustion in the engine cylinders. Atmospheric pressure is often inadequate to supply the required amount of air for proper operation of an engine.
An internal combustion engine, therefore, may include one or more turbochargers for compressing air to be supplied to one or more combustion chambers within corresponding combustion cylinders. The turbocharger supplies combustion air at a higher pressure and higher density than existing atmospheric pressure and ambient density. The use of a turbocharger can compensate for lack of power due, for example, to altitude, or to otherwise increase power that can be obtained from an engine of a given displacement, thereby reducing the cost, weight, and size of the engine required for a given power output.
A turbocharger typically includes a turbine driven by exhaust gases from the engine, and a compressor driven by the turbine. The compressor receives the air to be compressed and supplies the air to the combustion chamber. A common shaft interconnects the turbine wheel of the turbine with the compressor wheel in the compressor section. A stream of exhaust gases from the engine is conducted from the exhaust manifold to the turbine. The stream of exhaust gasses passing through the turbine causes the turbine wheel to rotate, thereby turning the common shaft interconnecting the turbine wheel and the compressor wheel and rotating the compressor wheel.
Several problems are experienced with previously known constructions for turbochargers as described above. For instance, turbochargers generally take some time to gain speed and provide increased pressure when increased power demands are placed on the system. This generally is the result of rotational inertia of the turbocharger. Therefore, when the engine is operating under conditions that require quick increases in power, a delay period occurs while the turbocharger accelerates and desired instantaneous increases in power cannot be achieved. This also holds true when the engine is operating under conditions that require quick decreases in power and pressure. Addition/removal of large electrical loads or xe2x80x9cblock loadsxe2x80x9d incurred while providing a constant rotational speed for the engine are an example of the transient loads that may require quick changes in power.
As the engine runs, the turbocharger will cycle through various ranges of rotational speed as power is added or removed. Because of the rotational inertia of the turbocharger, it is often necessary to run the engine at low efficiency to control heating of the exhaust flow during periods of transient loads, thereby controlling rotational speeds of the turbocharger. These low efficiency operations have the drawback of increasing the emissions of, for example, soot and nitrogen oxides.
One solution for providing a quick response is described in U.S. Pat. No. 4,312,183, entitled xe2x80x9cEXHAUST GAS TURBOCHARGER FOR DIESEL ENGINES,xe2x80x9d issued Jan. 26, 1982 This patent describes a turbocharger having a compressor, an exhaust gas turbine, and a shaft joining the exhaust gas turbine to the compressor. A flywheel is supported on a separate shaft and is coupled/uncoupled to the shaft of the turbocharger through a freewheel on the shaft. The shaft supporting the flywheel includes two portions that are connected through a summation device. However, this arrangement has several drawbacks including the number of additional components and the complicated interconnection between components.
The present invention solves one or more of the problems described above associated with existing turbochargers.
In one aspect of the present invention, a flywheel assembly for use with a supercharger having a rotatable shaft is provided. The flywheel assembly includes a flywheel configured to rotate about an axis of and be supported by the rotatable shaft and a clutch configured to selectively couple the flywheel to the rotatable shaft.
In another aspect of the invention, a turbocharger system is provided with a turbocharger including a turbine, a compressor, and a shaft connecting the turbine to the compressor. A flywheel assembly is supported by the shaft.
In yet another aspect of the invention, a method of operating a turbocharger system having a turbocharger is provided. The turbocharger may include a turbine, a compressor, and a shaft connecting the turbine to the compressor. The turbocharger system may also have a flywheel assembly supported by the shaft. The method includes supplying gas to the turbine to rotate the shaft, compressing gas via rotation of the compressor, and selectively engaging the flywheel assembly with the shaft to perform one of adding rotational energy to the turbocharger and removing rotational energy from the turbocharger.